2 Answers
2

First off, hope that you properly removed the links before so you can just snap the links back into place, that is easiest.

Any breaker that is designed properly will push the pin just to the point where you can snap the links out leaving the pin still attached.

Snap the removed links back onto the chain and place the chain back onto the breaker with the pin facing into the breaker like this:

Carefully push the pin back into the link making sure the breaker pin and the roller pin are aligned. Misalignment can cause damage to the chain and breaker. Only push the pin through until it is extended past the link as far as the pins in the rest of the chain:

Now the link will be too tight to bend easily, this is fixed by placing the chain in the middle jig and pushing the pin slightly, just enough to free the link up.

Test the link to be sure it bends easily. Now go back and remove the proper number of links, making sure the male/female links match up when the chain is looped with or without a master-link, your preference.

And if you didn't do that you can just take a piece of the offcut chain and use two smart-links/fast-links. s. you might want to cut the existing chain a bit short to take a long bit of spare chain so you don't have two removable links togetjer
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mgbAug 26 '12 at 20:13

Important point: If you need to make the chain longer by one link, don't detach one link from your "bit-o-chain" and try to attach it -- this will be unmanageable. Attach the entire "bit", then re-shorten the chain.
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Daniel R HicksAug 26 '12 at 20:45

Please excuse my ignorance. Can you do this with 10 and 11 spd chains? I don't have personal experience with this, but I've heard anecdotally that some 10 speed chains are too fragile for this and that you should discard the pin and use a master link.
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Mike SamuelAug 27 '12 at 4:14

I worked in a bike shop and never heard this, but most chains we worked on had master links (and rarely cut them wrong ;-). I learned how to do this on my own bikes before working there, but I always use the strongest chains I can find. I would suggest you post this as a new question, better answers AND boost your stats at the same time!
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BillyNairAug 29 '12 at 5:49

Pretty much all Shimano chains now use the special tapered pins for reassembly. And I've become a devotee of SRAM master links. But it doesn't hurt to learn how to do a chain repair "the old-fashioned way", in case you're ever stuck on the road with no other option.
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Daniel R HicksOct 5 '12 at 0:47

I'm a fan of master links too, but if I'd made a chain too short, I'd put it back with a normal pin. I'm still using chains without tapered pins though. And yes, if you are on the road with a broken chain, a chain tool, no spare master link, and no spare pin, you might have to reuse a pin that isn't designed for it or walk.
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armbOct 5 '12 at 12:18